media redundancy protocol (mrp)

Feature Overview and Configuration Guide

Technical Guide

Media Redundancy Protocol (MRP)

IntroductionThis guide describes Media Redundancy Protocol (MRP) and how to configure it.

Media Redundancy Protocol (MRP) is a protocol for providing redundancy in Ethernet networks via a

ring.

ContentsIntroduction .........................................................................................................................................1

Products and software version that apply to this guide ...............................................................2

Related documents.......................................................................................................................2

Licensing.......................................................................................................................................2

Media Redundancy Protocol Overview...............................................................................................3

What is it? .....................................................................................................................................3

Important concepts.......................................................................................................................3

How it works .................................................................................................................................3

Configuration examples ......................................................................................................................5

Switchport mode access ..............................................................................................................5

Switchport mode trunk .................................................................................................................7

Show commands ..............................................................................................................................10

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Products and software version that apply to this guide

This guide applies to AlliedWare Plus™ products that support MRP, running version 5.5.0-2.1 or

later.

To see whether your product supports MRP, see the following documents:

The product’s Datasheet

The product’s Command Reference

These documents are available from the above links on our website at alliedtelesis.com.

Most features described in this document are supported from AlliedWare Plus 5.5.0-2.1 or later. The

following features are available in later releases:

Version 5.5.1-1.1 and later support MRP in Virtual Chassis Stacking (VCStack) environments.

For more information on VCStack, see the Virtual Chassis Stacking (VCStack) Feature Overview and

Configuration Guide.

Related documents

The following documents give more information about MRP features on AlliedWare Plus products:

The product’s Command Reference

Licensing

An MRP license is required to use this feature. From AlliedWare Plus version 5.5.2-0.1 onwards, an

MRP license is required on the device that is an MRP manager. In earlier software versions, an MRP

license is required to run either MRP client or MRP manager.

To obtain a license, contact your authorized Allied Telesis representative.

C613-22127-00 REV C Introduction |

https://www.alliedtelesis.com/documents/virtual-chassis-stacking-vcstack-feature-overview-and-configuration-guide

https://www.alliedtelesis.com/documents/virtual-chassis-stacking-vcstack-feature-overview-and-configuration-guide

https://www.alliedtelesis.com/library/search/doctype/datasheets-2491

https://www.alliedtelesis.com/library/search/doctype/reference-guides-2436?search=command%20reference

https://www.alliedtelesis.com/library/search/doctype/reference-guides-2436?search=command%20reference

http://alliedtelesis.com


Media Redundancy Protocol Overview

What is it?

Media redundancy is primarily used to avoid single points of failure in industrial communication

networks. If a failure occurs on a redundant structure, the network falls back to a secondary state in

which communication is still viable, and repair can be made to restore the system to the previous

fault-free state.

Ethernet technology does not allow physical loops, as they cause packets to circulate endlessly and

overload the network. This means providing media redundancy within an Ethernet network requires

the use of a protocol that is able to monitor and resolve the physical loops introduced by redundant

pathways. This protocol must ensure that, even with multiple physical pathways to any device, only

one is activated at any one time and the remaining are in standby mode. This is achieved by:

monitoring links,

detecting interruptions, and

switching to an alternative path in the event of failure as soon as possible.

Media Redundancy Protocol (MRP) is a protocol for providing redundancy in Ethernet networks via a

ring. MRP is specified for ring networks with up to 50 devices. It guarantees fully predictable switch-

over behavior. Allied Telesis switches support worst-case switch-over times of 200 or 500ms.

Important concepts

MRP node: A switch contained within a ring network monitored by MRP.

Redundancy Domain: A ring controlled by MRP.

Media Redundancy Manager (MRM): A single MRP node that monitors and controls the ring

network and reacts to any failure.

Media Redundancy Client (MRC): Any node within the ring that is not an MRM.

Ring port: The two designated ports on each MRP node that are physically connected to the ring

topology.

How it works

Ring ports can be in one of three states:

disabled: all packets received by the port are dropped.

blocking: all packets received by the port are dropped, with the exception of MRP protocol

packets.

forwarding: all packets received by the port are forwarded.

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The ring itself can be in one of three states:

closed: both ports on all nodes are linked up, one port on the MRM is blocking, all others are

forwarding.

open: both ports on the MRM are forwarding, either because one of the MRCs has signalled a

port down, or the MRM failed to receive its own test frames.

undefined: this is set before the actual state of the ring is known.

MRM port blocking

During normal operation, one of the MRM’s ring ports is blocking, while the other is forwarding.

This puts the network in a closed state, where the physical ring topology is in a ring structure, and at

the logical level is in a linear structure. The MRM sends MRP_Test frames (at a predetermined

interval) out both its ring ports. These will be forwarded around the ring by the MRCs until they again

reach the MRM.

In the case of a transmission failure (for example, a ring port becomes disabled), the MRM will fail to

receive its test frames. After a predefined number of test packets are lost, it will set its blocking ring

port to forwarding. This enables the secondary network path, and puts the network in an open

state where both MRM ring ports are forwarding.

MRC port blocking

MRP rings support two profiles for recovery time, 200ms or 500ms. This is set with the profile (mrp-

ring) command.

If the MRP ring is set to the 200ms profile, it also uses port blocking on the MRCs. When an MRC

detects a link down on one of its ports, it puts the port in a blocking state. This is to prevent a loop

if and when the port comes back up again, since the MRM has unblocked its secondary port. When

the port comes back up, the MRC signals the MRM with an MRP_Link_Up frame. This contains the

MRP_LNKupT interval that tells the MRM when the MRC is going to unblock its port. The MRM then

blocks its secondary port after the same interval. Both nodes doing this at the same time minimizes

any interruption, while still preventing loops.

If the MRP ring is set to the 500ms profile, port blocking is not used.

All nodes in an MRP ring must be set with the same profile.

Virtual chassis stacking

Virtual Chassis Stacking—VCStackTM —is the name given to two or more Allied Telesis switches that

are configured to operate as a single switch. From a configuration and management point of view, it

is as though the switches are just one device with a seamless transition from the ports of one stack

member to the ports of the next. VCStack provides a highly available system where network

resources are spread out across stacked units, reducing the impact if one of the units fails.

Aggregating switch ports on different units across the stack provides excellent network resiliency.

For more information on VCStack, see the Virtual Chassis Stacking (VCStack) Feature Overview and

Configuration Guide.

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Configuration examplesThe switchports in an MRP ring can be configured in either access or trunk mode. All nodes in the

ring must be configured in the same mode. We recommend configuring in access mode, unless you

have a setup that requires trunk mode (for example, if you need to send tagged Ethernet frames for

any other device or switch on a port).

Each node in the ring must be configured with the same domain-id UUID. By default, this is set

based on the ring ID, using the value:

(FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF) - (ring ID + 1)

You can check the UUID by using the show mrp ring command, and set it using the domain-id

command.

From AlliedWare Plus version 5.5.2-0.1 onwards, an MRP license is required on the device that is an

MRP manager. In earlier software versions, an MRP license is required to run either MRP client or

MRP manager.

Switchport mode access

The following examples show how to configure an MRP ring with the switchports in access mode.

Media redundancy manager (MRM) configuration

Step 1: Start the MRP service

awplus#configure terminal

awplus(config)#service mrp

The MRP service needs to be started before any other MRP configuration.

Step 2: Create the MRP ring

awplus(config)#mrp ring 1

This command creates an MRP ring with the ring ID 1, and enters MRP Configuration mode.

Step 3: Set the role to manager

awplus(config-mrp-ring)#role manager

This command sets the role of this node to manager for your MRP ring, and enters MRP Ring

Manager Configuration mode.

Step 4: Select the ring ports

awplus(config-mrp-ring-manager)#end


awplus(config)#interface port1.0.25,port1.0.29

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Return to Global Configuration mode, then select the ring ports to configure. In this example, we are

configuring port1.0.25 and port1.0.29.

Step 5: Configure the ring ports

awplus(config-if)#switchport mode access

awplus(config-if)#mrp ring 1

These commands set the switchport mode to access, and attach MRP ring 1 to port1.0.25 and

port1.0.29. When the ports are set to access mode, the MRP ring will use the VLAN of the ports.

This is an example of the configuration for an MRM in an access mode MRP ring.

Media redundancy client (MRC) configuration on every other switch in the ring









awplus(config-mrp-ring)#end






awplus(config-if)#switchport mode access


These commands set the switchport mode to access, and attach MRP ring 1 to port1.0.25 and

port1.0.29. When the ports are set to access mode, the MRP ring will use the VLAN of the ports.

!service mrp!mrp ring 1 role manager!interface port1.0.25,port1.0.29 switchport switchport mode access mrp ring 1!



This is an example of the configuration for an MRC in an access mode MRP ring.

Switchport mode trunk

The following examples show how to configure an MRP ring with the switchports in trunk mode.

Media redundancy manager (MRM) configuration

Step 1: Create the VLAN


awplus(config)#vlan database

awplus(config-vlan)#vlan 10

awplus(config-vlan)#end

These commands create a VLAN named 10.








Step 4: Set the role to manager

awplus(config-mrp-ring)#role manager

This command sets the role of this node to manager for your MRP ring, and enters MRP Ring

Manager Configuration mode. This command requires an MRP license on this device.

Step 5: Assign the VLAN

awplus(config-mrp-ring)#vlan-id 10

This command assigns the VLAN 10 to the MRP ring. When the ports are set to trunked mode, then

the VLAN must be assigned to the MRP ring using the vlan-id command.

!service mrp!mrp ring 1!interface port1.0.25,port1.0.29 switchport switchport mode access mrp ring 1!




awplus(config-mrp-ring-manager)#end






awplus(config-if)#switchport mode trunk

awplus(config-if)#switchport trunk allowed vlan add 10


These commands set the switchport mode to trunk, set VLAN 10 to be trunked, and attach MRP

ring 1 to port1.0.25 and port1.0.29.

This is an example of the configuration for an MRM in a trunk mode MRP ring.

Media redundancy client (MRC) configuration on every other switch in the ring

Step 1: Create the VLAN


awplus(config)#vlan database

awplus(config-vlan)#vlan 10

awplus(config-vlan)#end

These commands create a VLAN named 10.







!service mrp!mrp ring 1 vlan-id 10 role manager!vlan database vlan 10 state enable!interface port1.0.25,port1.0.29 switchport switchport mode trunk switchport trunk allowed vlan add 10 mrp ring 1!




Step 4: Assign the VLAN

awplus(config-mrp-ring)#vlan-id 10

This command assigns the VLAN 10 to the MRP ring. When the ports are set to trunked mode, then

the VLAN must be assigned to the MRP ring using the vlan-id command.


awplus(config-mrp-ring)#end






awplus(config-if)#switchport mode trunk

awplus(config-if)#switchport trunk allowed vlan add 10


These commands set the switchport mode to trunk, and attach MRP ring 1 to port1.0.25 and

port1.0.29.

This is an example of the configuration for an MRC in a trunk mode MRP ring.

!service mrp!mrp ring 1 vlan-id 10!vlan database vlan 10 state enable!interface port1.0.25,port1.0.29 switchport switchport mode trunk switchport trunk allowed vlan add 10 mrp ring 1!



Show commands

Example output from the show mrp ring command:

Table 1: Parameters in the output from the show mrp ring command

awplus#show mrp ringMedia Redundancy Protocol - Ring InformationMRP Ring 1 Domain ID: ffffffff-ffff-ffff-ffff-ffffffffffff Domain Name: Ring Status: Enabled Operating Mode: CLI Role: Manager Network Status: Open Port1: port1.0.25 Status: Forwarding Port2: port1.0.29 Status: Forwarding

Vlan ID: React on Link Change: No Profile: 200ms Topology Change Interval: 10ms Topology Change Count: 3 Short Test Frame Interval: 10ms Default Test Frame Interval: 20ms Test Monitoring Interval Count: 3 Test Monitoring Ext Interval Count: 0 Non-blocking MRC Supported: No

PARAMETER DESCRIPTION

Domain ID The UUID that identifies the ring.The Domain ID is used in MRP PDU packets.

Domain Name Description of the ring that can be set by the user.

Ring Status Whether the ring is Enabled or Disabled.

Operating Mode CLI - the MRP ring is configured and controlled from the command line.

Role Whether the node is a Manager (MRM) or Client (MRC).

Network Status Whether the MRP ring is Open or Closed (MRM only).

Port Status The state of the port:Disabled - all packets received by the port are dropped.Blocking - all packets received by the port are dropped, with the exception of MRP protocol packets.Forwarding - all packets received by the port are forwarded.

Vlan ID If the MRP ring is configured with a trunked VLAN, this shows the configured VLAN ID.

Profile Whether it is configured for 200ms or 500ms.

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Example output from the show mrp ports command:

Table 2: Parameters in the output from the show mrp ports command

awplus#show mrp portsMedia Redundancy Protocol - Port Information

Connection Port State------------------------------------------Ring 1 port1.0.25 ForwardingRing 1 port1.0.29 Blocking

awplus#awplus#show mrp portsMedia Redundancy Protocol - Port Information

Connection Port State------------------------------------------Ring 1 port2.0.25 ForwardingRing 1 port2.0.29 Forwarding


Connection The name of the MRP ring.

Port The ID of the port.

State The state of the port:Disabled - all packets received by the port are dropped.Blocking - all packets received by the port are dropped, with the exception of MRP protocol packets.Forwarding - all packets received by the port are forwarded.



Example output from the show counter mrp command:

Table 3: Parameters in the output from the show counter mrp command

awplus#show counter mrpMedia Redundancy Protocol Global Counters

MRP Started ....... 1MRP Dispatcher ....... 16574983MRP Timer Tick ....... 16446942MRP Packet RX ....... 128041MRP Packet RX Error ....... 0MRP Packet TX ....... 1642783MRP Packet TX Error ....... 0

Media Redundancy Protocol Ring 1 Counters

Port 1 PDUs ReceivedMRP_Test ......... 64013MRP_TopologyChange ......... 0MRP_LinkUp ......... 0MRP_LinkDown ......... 0

Port 1 PDUs TransferredMRP_Test ......... 821366MRP_TopologyChange ......... 26MRP_LinkUp ......... 0MRP_LinkDown ......... 0

Port 2 PDUs ReceivedMRP_Test ......... 64013MRP_TopologyChange ......... 0MRP_LinkUp ......... 15MRP_LinkDown ......... 0

Port 2 PDUs TransferredMRP_Test ......... 821366MRP_TopologyChange ......... 26MRP_LinkUp ......... 0MRP_LinkDown ......... 0

Other CountersState Changes ......... 11Port Blocked Set ......... 6Port Forwarding Set ......... 5Multiple Manager ......... 0


MRP Started The number of times the MRP service has been started with the service mrp command. This counter increases each time it is stopped and started.

MRP DispatcherMRP Timer Tick

Internal timer tick that provides timing for the protocol and the dispatcher. This is called to process timing events, packet reception, and state changes.

MRP Packet RX The number of MRP protocol packets received.

MRP Packet RX Error The number of failures when receiving a packet.

MRP Packet TX The number of MRP protocol packets sent.

MRP Packet TX Error The number of failures when sending a packet.


MRP_Test The number of test frames sent and received by the Media Redundancy Manager (MRM) to test if the ring is open or closed.

MRP_TopologyChange The number of topology change frames sent from the MRM to indicate ring topology changes to Media Redundancy Clients (MRC).

MRP_LinkUpMRP_LinkDown

The number of Link Up/Down frames sent from MRC to indicate a link state change on one of its ring ports.

State Changes The number of changes in the protocol state. These are triggered by test packets detecting the ring opening or closing, and MRP ring port link changes.

Port Blocked Set The number of times a ring port has been set to blocking.

Port Forwarding Set The number of times a ring port has been set to forwarding.

Multiple Manager A misconfiguration detected by the MRM that another manager is on the ring. This is detected from information in the MRP PDU frames.


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